Total Report With No Appendix

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Fina l Thesis Report

UniversityofMarylandCollegeParkDormBuilding7

CollegePark,MD

PreparedBy:RyanSolnoskyStructuralOptionMAE/BAEFacultyAdvisor:Dr.AliMemari

April7,2009

ThePennsylvaniaStateUniversity

DepartmentofArchitecturalEngineering

SeniorThesis20082009


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Ryan Solnosky UMCP Dorm Building 7Structural Option Dr. Memari

Final Report Page 2 of 127

Foundation Implications ................................................................................48Cost Considerations .......................................................................................51Structural Design Summary ...........................................................................52

Goal Evaluation ..................................................................................53

Breadth StudiesBreadth 1: Green Roof Design

Materials and Considerations .............................................................54Roof Layout .......................................................................................55Water Collection Design ....................................................................56LEED and Benefits ............................................................................57

Breadth 2: Acoustic StudySound Isolation Verification ..............................................................58Advanced Measures in Isolating Noise .............................................60

Conclusions ................................................................................................................61

AppendixA: Wind Load Calculations ...........................................................................63B: Seismic Load Calculations .......................................................................66C: Gravity Spot Checks .................................................................................69D: Lateral Spot Checks .................................................................................88E: Breadth Topic 1: Green Roof Design .......................................................106F: Breadth Topic 2: Acoustic Study ..............................................................113G: Building Plans ..........................................................................................117H: Bibliography .............................................................................................126


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Executive Summary

The University of Maryland College Park Dorm Building 7 (Building 7) is the final stageof the south campus master plan at the University of Maryland. Building 7 is an eight story

residential dorm in the shape of an unsymmetrical-U that compliments the adjacent two existingdorm buildings in architectural styles with its shape and material usage. This eight story-133,000square feet residential building, houses 370 bedrooms, study lounges, seminar spaces andresident life offices. The layout of each floor is such that all of the rooms have an exterior viewof the surrounding campus with a central corridor running the length of the building. The rooflevel houses the mechanical equipment along with the elevator and stair towers. Building 7 isalso in the process of achieving a LEED Gold rating.

This report includes a seismic analysis of the Building 7 which the location was moved toSan Diego, California which has a high seismic activity. San Diegowas chosen based on itsseismic activity and also because the San Diego Region has a University, The University of

California at San Diego, since this building is a dorm this location makes it a good choice if USDwould ever want a new dorm.

Building 7 was redesigned from the original Hambro Composite Joists and bearing wallswith light gage shear walls to a more standard and reliable structural steel system. Structural steelwas chosen for back in Technical Report 2 it was determined to be the most efficient for the cost.A new bay layout and also the locations of the new Special Concentric braced Frame had to bedetermined. A double loaded corridor was determined to be the best bay layout and the redesignwas able to reduce the number of lateral frames as compared to the original (16 before to 10 atthe end). Lateral connections were looked and were designed to meet the seismic requirements.

The AISC Steel Construction Manual, 13th Edition and Steel Seismic Design Manualwere used as a basis for all of the structural steel designs. A Ram Structural Model was createdto help with the analysis and the design of both the gravity and the lateral systems. Preliminaryhand calculations and spot checks were performed to verify the computers results to ensure thedesign was valid. ASCE 7-05 was used to determine the required seismic loads and conditionsalong with all the other loading and general requirements. Advanced computer modeling alongwith connections were looked at for the MAE requirement.

Two breadth studies were conducted; the first was a green roof study. A green roof wasdesigned to bring and add to the Green Standard and make the building more efficient. A watercollection was also designed for both locations so that the roof runoff can be used to help reduce

the water consumed by the sanitary system. The second breadth study was an acoustic study tosee the impacts of changing the structural system to steel. It was determined that the new systemis acceptable and recommendations were made to make the space more efficient at reducingsound leaks throughout.


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Acknowledgements

Facility

Dr. Ali Memari Dr. Andres Lepage

Professor M. Kevin Parfitt

Dr. Moses Ling

Companies and Professionals

Hope Furrer Associates, Inc.

Hope Furrer

Melissa Harmon

Heather Sustersic

Design Collective

Nick Mansperger

Burdette, Koehler, Murphy & Associates

Emily Trumbull

Yefim Rubin

Family and Friends

Id like to thank all friends and family who helped me through this time for this project by givingme support and help when it was need or asked for. Id especially like to thank:

Parents

Simon Miller

Kim McKitish

Joe Wilcher


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Building Overview

The University of Maryland College Park Dorm Building 7 (Building 7) is the final stageof the south campus master plan at the University of Maryland. Building 7 is the corner stone of

the south campus entrance for all to take part of as they approach the campus. Building 7 is aneight story residential dorm in the shape of an unsymmetrical-U that compliments the adjacenttwo existing dorm buildings in architectural styles with its shape and material usage.

Architecture

This eight story-133,000 square feetresidential building, houses 370 bedrooms, studylounges, seminar spaces and resident life offices.The average floor to floor height is 10 feet on eachfloor with an average floor area of 12,000-15,500

square feet per floor, depending on shifts in thevertical plane. The layout of each floor is such thatall of the rooms have an exterior view of thesurrounding campus with a central corridor runningthe length of the building. The roof level houses themechanical equipment along with the elevator andstair towers.

The faade and building envelope iscomprised of light gage studs with a brick masonryveneer exterior around the entire building. There is

rigid insulation on the exterior of the studs betweenthe veneer with a 1.5 inch air cavity. The walls arefilled with batt insulation and covered in drywall.

The windows are fixed casement aluminumwindows with cast stone sills to accent them. In the regions where the wall sections are pulledaway from the primary facade, the wall system is composed of composite metal panel and caststone veneer panels. The roof system is an EPDM classification which is a fully adhered systemcomprised of a waterproof membrane that is bonded to rigid insulation by mechanical andchemical means with appropriate flashing at the base of the parapets and where the brick meetsthe top of the parapet.

Mechanical System

Building 7s mechanical system is for a residential space requirements with small areasusing office requirements where needed. The corridors of Building 7 utilize two rooftoppackaged heat pumps that supply heating cooling and ventilation to the corridors. Apartmentsand community areas utilize split system closet type heat pump units that provide heating andcooling only. Ventilation to these areas is not mechanically supplied but instead there is natural


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ventilation by the means of operable windows. The reason for this is to help gain LEED points.The exterior walls were also carefully designed to limit the amount of heat loss and gain throughthem, to better control the inside environment.

The mechanical heating and cooling units are all located on the roof level of Building 7

and there are 101 units on a concrete curb. The split system heat pumps have a range of 500-1500 CFM depending on the space they support. The packaged rooftop units on the north sidesupply 1680CFM while the south side units supply 2800 CFM. The stairwell pressurization fansfor fire emergencies produce 9000 CFM for each stairwell and are run on the fire alarm system.

Electrical System

Building 7s electrical system is powered by PEPCO and they design as well as install theprimary underground cables to the pad mounted transformer. The secondary cables to thebuilding distribution system will be handled by the utility company. The service voltage will be480/277-volt, 3-phase, 4-wire, and 60 hertz. The main distribution switchboard (SWBD) is rated

at 2500 amperes, 480/277V, 3-phase, and 4-wire. This switchboard will include a manuallyoperated insulated case stationary main circuit breaker with an adjustable solid state trip unit.

The distribution system will stem from the SWBD with feeders to panels on each floor.A separate 208/120-volt, 3-phase, 4-wire feeder will provide power to the residential distributionpanel on each floor. There is not residential sub-metering for the individual loads in each livingunit. A 208/120-volt, 1 phase, 3 wire load center will be located within each living unit and willbe dedicated to all the electrical loads within the associated unit.

Construction Management

The construction of Building 7 started on July 21, 2008 and is expected to be finished inJanuary 2010. The construction manager for the project is Whiting-Turner Contracting; they aretaking on the role of CM at Risk. The total cost of the project is at $23.5 million with andestimated structural system cost of 3.98 million at the current time.Due to the size of the site, theconstruction team was permitted to set-up their trailer complex nearby on an existing parking lot.This area provides more space for field offices and a staging site.A Tower crane will most likelybe employed as it would avoid any coordination and traffic maintenance around the site. Noother details can be given at this time due to the early stages of construction.

Lighting System

The lighting system primarily uses fluorescent lighting fixtures throughout the building.The corridors are lighted by 2x2 277V parabolic fluorescent fixture with electronic ballast with a32 watt lamp. The seminar room uses the same style fixture except it is a 2x4 and has a dimmerballast. The apartment units are comprised of 8 compact fluorescent downlights with electronicballasts in the common living areas and surface mounted fluorescent with a contoured acrylicdiffuser, both of these fixtures run on 120V. The entrance lobby is accented with 8 fluorescentdownlight wallwashers and 8 recessed fluorescent fixtures.


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Existing Structural Systems Conditions

Foundation

The foundation system is composed of reinforced concrete grade beams 24x30 with3#8s on the top and bottom with number #4 stirrups placed every 14. The deep foundationportion is auger cast grout piles 16 in diameter. These piles are to be 65 below elevation andare to be able to carry at 65 ton allowable load capacity. The pile configurations range from 2-4piles per cap. The slab on grade for the foundation is 4 thick normal weight concrete reinforcedwith 6x6-1.4xW1.4 welded wire fabric. All foundation concrete is 4ksi except for the SOGwhich is 3.5 ksi. Due to the sites soil conditions it was necessary that the differential settlementover the entire building was limited, because of this the allowable soil bearing capacity was heldto 500 psf.

Column and Bearing Wall Systems

The concrete columns support the lower two floors ofBuilding 7. They arranged to form a typical bay of 15x20.These columns are gravity bearing only due to the type oflateral system in the building. The typical size of the columnsrange from 18x14 to 64x14 with the reinforcing ranging in eachfrom 4#9s to 10#9s for vertical bars with #4 stirrups spaced at14 O.C.. The concrete compressive strength for the columns is6 ksi.

The bearing walls in Building 7 support the upper 6floors and run along the outside perimeter of the building as

well as along the corridors. The typical spans for the floor joistsare 20. Dealing with the concerns that the joists may not lineup with the studs causing the header to buckle, this problemwas solved by placing a distribution tube across the tops of allbearing walls. These walls are also to be designed by the contractor who is given general criteriato follow along with a loading diagram for all the different bearing walls. The general criteriaare: a maximum stud spacing of 16 O.C., a minimum G90 galvanized coating, and have aminimum 16 gage thickness.

Roof System

The roof system is made of the same Hambro Composite Floor System bearing on lightgage walls. This Hambro Composite Floor System is also to be designed by the contractorinstead of the Engineer just as the other floors are to be designed. Here are the criteria for theroof: overall depth of the members is 16 deep typically throughout except in the corridors whichit drops to 8deep with a 3 thick concrete slab reinforced with 6x6-2.9xW2.9 welded wirefabric. The mechanical unit weights are listed and are placed close to the corridors for they areformed by the bearing walls. The elevator towers and stair towers are made of the same lightgage studs.


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Floor Systems

Lower 2 Floors

The lower two floors are made of reinforced concrete beams spanning between thecolumns. The intermediate members between these beams are made up of the HambroComposite Floor System, which includes the steel joists and the slab system. The concrete beamsrange from 16x36 to 18x18 to 24x36 with the reinforcing ranging in each from 3#5s to 6#10sfor longitudinal bars with #4 stirrups spaced from 8 to 16 O.C.

The Hambro Composite Floor System in Building 7 is not designed by the StructuralEngineer but rather is to be designed by the Contractor. The Structural Engineer has howevergiven detailed criteria that the contractor must follow. The following is the criteria: are overalldepth of the members is 16 deep typically throughout except inthe corridors which it drops to 8deep, the slab on top is to be5 thick reinforced with 6x6-W4.0xW4.0 welded wire fabric.

Upper 6 Floors

The floor system is made of the same Hambro Floor System butinstead of them bearing on concrete girders they bear on light-gage stud bearing walls. This Hambro Floor System is also tobe designed by the contractor instead of the Engineer. Here arethe criteria for these 7 stories: overall depth of the members is16 deep typically throughout except in the corridors which itdrops to 8deep with a 3 thick concrete slab reinforced with6x6-2.9xW2.9 welded wire fabric.

Lateral Systems

The primary lateral system for Building 7 is shear walls. On each floor there are 16 shearwalls spanning both directions of the building, 9 in the north-south direction and 7 in the east-west direction. The lower two stories shear walls are 10 thick reinforced concrete with 10#5son each end for flexure and for shear reinforcement there is #5@12 each way, each face. Allconcrete shear walls are 6 ksi normal weight concrete. The upper floors shear walls are to belight gage studs with maximum stud spacing of 16 O.C. they are also have a minimum G90galvanized coating and have a minimum gage of 16 for the studs while the tracks are permitted

to have a 20 gage minimum. There is to be bridging at 4 spacing throughout the shear walls.Since these are light gage it was determined that steel strapping was needed and is beingprovided in an X pattern connecting to the farthest opposite ends. The light-gage shear walls notdesigned by the Structural Engineer but rather is to be designed by the Contractor. The StructuralEngineer has however given detailed loading diagrams of each load and the type of load on everyshear wall.


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Structural Depth Study

Problem Statement

The present design of Building 7 utilizes primarily propriety systems as the structure foras much as the materials will allow. These systems, while they may be cheaper require long leadtimes while also the general contractor to is required to design them. The propriety systems usedinvolve many miscellaneous metal supports for the lack of strength in the light-gage studs. Frominvestigating these systems in the past technical reports noise, vibration, and fire proofing issuesarise that makes these system less desirable.

These systems prevent the multiple floors from being build before the inner walls areplaced (due to so many bearing walls). This issue increases the construction time. The low floorto floor heights (10 with an 8 ceiling) are an issue for placing the structural elements and alongwith the MEP systems within the floor cavity. Finally the current system as 16 shear walls due tolight-gage cannot take a large amount of shear. Also the location of Building 7 is in a regionwhere the Seismic Design Category is A, which allows for a simplified approach. This categoryalmost entirely eliminates the need for seismic design and checking for the resulting forces are somuch smaller than wind.

Problem Solution

In an effort to address the issues stated above a redesign of the structural system is beingproposed in steel. This redesign will include both a gravity system and a lateral system. Thegravity system will take a look at two systems composite steel and composite castellated beams.An initial study will be made to see which is best when looking at the thin ceiling cavity to allowfor more space for the MEP systems. After the better choice has been determined that systemwill be further developed and used throughout the rest of the structural redesign. All steel gravityframing will be designed to conform to AISC Manual of Steel Construction, 13th Edition.

In regarding the lateral design and also the seismic issue it was decided that moving thebuilding to a high seismic zone located somewhere, to be determined, in California will takeplace. The lateral system will be redesigned after a study of the different types of lateral systems

that are acceptable in high zones and their benefits and shortcoming will be considered. After asystem is selected an optimum layout with hopefully fewer elements in plan can be resolved. Itshould also be noted that since the material has been changed to steel and that the site is beingmoved a represented new geo-technical report will be use and for this reason a detailed study onthe foundations can not be addressed in the given time but will be looked at in general overallaspects of the new steel system.

Problem Statement and Solution


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Design an overall structure made of steel and has limited use of propriety systems.

Design a gravity system that does not require a change in the building height while stillbeing acceptable.

Move the location of Building 7 to a high seismic to better understand and work withseismic requirements in detail.

Pick a single lateral system that will work for the new location and design it while tryingto optimize it.

Structural Goals


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Gravity Loads

Live Loads

The live loads used in this study and the report regarding Building 7 were calculated inaccordance with IBC 2006 which references ASCE 7-05, Chapter 6. In the event that ASCE didnot list loads needed a close equivalent was chosen to meet that particular space or condition.The table listed below summarizes the lives loads used.

Live Loads

Occupancy Design LoadCode Required Loads

Load Code

Corridors 100 psf 100 psf ASCE 7

Offices 50 psf 50 psf ASCE 7

Seminar Room 100 psf 40 psf ASCE 7Mechanical Room 125 psf 125 psf ASCE 7

Partition 20 psf - -

Roof 100 psf 100 psf ASCE 7

Dormitory Rooms 40 psf 40 psf ASCE 7

Lobby 100 psf 100 psf ASCE 7

Staris and exit ways 100 psf 100 psf ASCE 7

Dead Loads

The dead loads used in the study and the report regarding Building 7 were determined byreferencing various standards and textbooks to find the corresponding values for their weights.

Approximate values were assumed when ranges were listed depending on how dense the layoutswere and the authors personal preference as well as considering the life history and usage of thebuilding.

Dead Loads

Roof Dead LoadMaterial Design Weight

Green Roof 50 psf wet

Structural Members 15 psf

Floor Slab 46 psf

M/E/P 5 psf

Ceiling Finishes 5 psf

Total Dead Load 121 psf

Typ. Floor Dead LoadMaterial Design Weight

Structural Members 15 psf

Floor Slab 46 psf

M/E/P 5 psf

Ceiling Finishes 5 psfTotal Dead Load 71 psf

Building Loads


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Lateral Loads

Wind Loads

All wind loads were calculated in accordance with ASCE 7-05, Chapter 6. The analyticalmethod 2 was used to examine lateral wind loads in the North/South direction as well as theEast/West direction. Also due to the irregular shape of the building it was necessary to look atthe most critical orthogonal for it could possibly control, this was taken into consideration duringthe modeling process and a Ram Structural System load case was auto generated so to quickenthis process of finding the critical angle.

Building 7 is categorized as Exposure B due to its urban setting and location in SanDiego, CA. The basic wind speed was found to be 85 mph per Figure 6-1 in ASCE 7. Thebuilding is not quite a square relative to the four directions, with the N/S direction (169-8)slightly longer than the E/W direction (133-6). When inputting the wind forces in the computer

model the wind loading cases dictated in Chapter 6 and illustrated in Figure 6-9 was done. Allfour of the load cases were inputted.

Wind pressure step diagrams were drawn of the final forces acting on the building. Alsostory forces and story shears were calculated by hand to compare to the computer modelscalculation. Based on reviewing the model it was determined that the same values werecalculating it making its wind calculations valid. These diagrams can be found on the next pagewhile the calculations and wind criteria can be found in Appendix A.


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Wind Pressures

Wind Pressure Distribution in the North-South Direction Wind Pressure Distribution in the East-West Direction

All Values on Wind Pressure Step Diagrams are in pounds per square foot (psf). The Blue indicates windward andthe red indicate leeward pressures.

Wind Story Forces and Story Shears

Story Force and Shear in the North-South Direction Story Force and Shear in the East-West Direction


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Seismic Loading

The seismic loads were calculated in accordance with ASCE 7-05, Chapter 12 andreferencing Chapter 22. Since moving the building to San Diego it was clearly seen that the

original Simplified method for Seismic Design Category A was not going to be valid, thisresulted in a more rigorous method of calculating the seismic forces. After looking at therepresented geotechnical report for the San Diego Region, it was concluded that the building siteis very stiff to hard clays at the ground level with bedrock at the deep foundation level, resultingin a Site Class B. The new site location was determined to be Seismic Design Category D. todetermine the lateral forces and also the allowed procedure that can be used in Seismic DesignCategory D many conditions had to be met and considered. The rest of this section of the reportdescribes the findings of the conditions as well as the lateral forced used for the design.

Structural Irregularities

Section 12.3 of the ASCE 705 code determines and dictates the limitations fordiaphragm flexibilities and also determines what a structural irregularity is on the horizontal andthe vertical planes of the building. Table 12.6-1 gives the permitted analytical procedures foreach design class along with the limitations due to a structural irregularity.

Horizontal structural irregularities were determined according to Section 12.3.2.1. Thedescriptions of the horizontal irregularities are listed in Table 12.3-1. The following summarytable below represents each irregularity type and its regard to Building 7.

Horizontal Structural Irregularities

Type Irregularity Comment Status

1a TorsionalAfter Modeling structure it can been

concluded that this irregularity does notexist.

Good

2 Reentrant Corner

This irregularity does exist due to the U-Shape of the plans but ELFP is allowed, a

25% force increase for the connectionsbetween the diaphragm and the vertical

elements are required.

Not Met

3 Diaphragm DiscontinuityIrregularity does not exist by inspection of

the drawings.

Good

4 Out of plane OffsetsNo vertical element out of plane offsets

exists by inspection of the drawing.Good

5 Non Parallel SystemAll lateral force resisting systems are

parallel to the orthogonal axes.Good


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Vertical structural irregularities determined according to Section 12.3.2.2. Thedescriptions of the vertical irregularities are listed in Table 12.3-2. The following summary tablebelow represents each irregularity type and its regard to Building 7.

Vertical Structural IrregularitiesType Irregularity Comment Status

1a StiffnessSoft StoryMembers are larger going down the

building, plus calculations were done toprove it in a later section.

Good

2 Weight (Mass)Was carefully looked at due to the greenroof and Mechanical Units but roof was

approx. 400 kips under limit.Good

3 Vertical GeometricPlans show same geometry the height of

the building.Good

4InPlane Discontinuity of

Vertical Lateral ForceResisting Element

No discontinuity exists by inspection of thedrawings.

Good

5a, bDiscontinuity in Lateral

StrengthMembers are upsized going down thebuilding resulting in a higher strength. Good

After looking at the structure and the limiting factors that govern the analytical proceduredetermined by Section 12.6, it was found that the structure is considered regular with only oneirregularity in which the diaphragm connections need a 25% increase in their force (ELFPpermits this) and since T


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Lateral System Criteria (Special Concentric Braced Frames)

The lateral system being looked at for the lateral redesign of Building 7 is the SpecialConcentric Braced Frame, which the reason for this lateral system is discussed in detail in the

Lateral Study section. To compute exact values for Ss and S1 the United States GeologicalSurveys software under NEHRP design provisions was used. The table below summarizes theseismic criteria and its associated values along with what part of the relevant code was sued fordetermining it. Refer to Appendix B for more detailed spreadsheets and along with the Cscalculations.

Seismic Criteria for SCBF Design

Criteria Value CodeReferenceOccupancy Category II Table 1.1

Importance Factor 1.000 Table 11.51Seismic Category D ASCE 7-05 Section 11.6

Site Class C Geotechnical Report

Spectral Acceleration for Short Periods (Ss) 1.572 www.usgs.org

Spectral Acceleration for 1 Second Periods (S1) 0.617 www.usgs.orgSite Coefficient, Fa 1.000 ASCE 7-05 Table 11.41Site Coefficient, Fv 1.300 ASCE 7-05 Table 11.42

Seismic Design Category D ASCE 7-05 Table 11.61,2R Factor 6.000 ASCE 7-05 Table 12.2-1 # B3

SMS 1.572 ASCE 7-05 Equation 11.4-1SM1 0.802 ASCE 7-05 Equation 11.4-2SDS 1.048 ASCE 7-05 Equation 11.4-3SD1 0.535 ASCE 7-05 Equation 11.4-3

Deflection Amplification Cd 5.00 ASCE 7-05 Table 12.2-1 # B3Overstrength Factor 2.00 ASCE 7-05 Table 12.2-1 # B3


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Vertical Force Distribution for SCBF

The vertical distribution of the seismic based shear is determined by ASCE7-05 Section12.8.3 the force at any given floor is based on a distribution factor times the total design base

shear. After the Cs factor was determined by Section 12.8.1.1 and the overall weight of thebuilding was calculated the seismic base shear was determined the distribution factor wascalculated and the tables below represent the vertical forces. The reason for the different forcesin each direction was due to an adjustment in the north south direction when the actual periodwas inputted after the structure was initially designed. After this the new forces were placed inthe model again and final designs were worked out.

Vertical Force Distribution E-W Direction

Floor Height (Ft.) Weight (Kips) Cvx Fx (kips) Story Shear

Roof 90 2145.00 0.24 398.08 398.08

8 80 1700.00 0.17 280.44 678.52

7 70 1700.00 0.15 245.39 923.916 60 1700.00 0.13 210.33 1134.24

5 50 1700.00 0.11 175.28 1309.51

4 40 1700.00 0.08 140.22 1449.73

3 30 1700.00 0.06 105.17 1554.90

2 20 1700.00 0.04 70.11 1625.01

1 10 1700.00 0.02 35.06 1660.06

Total Weight 15745 kips

Seismic Base Shear 1660.06 kips

Overturning Moment 107,339.65 kip-ft

Vertical Force Distribution N-S Direction

floor Height (Ft.) Weight (Kips) Cvx Fx (kips) Story Shear

Roof 90 2145.00 0.24 467.42 467.42

8 80 1700.00 0.17 329.29 796.70

7 70 1700.00 0.15 288.12 1084.83

6 60 1700.00 0.13 246.96 1331.79

5 50 1700.00 0.11 205.80 1537.59

4 40 1700.00 0.08 164.64 1702.24

3 30 1700.00 0.06 123.48 1825.72

2 20 1700.00 0.04 82.32 1908.04

1 10 1700.00 0.02 41.16 1949.20

Total Weight 15745 kips

Seismic Base Shear 1949.20 kips

Overturning Moment 126,035.22 kip-ft


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Gravity System Considerations

When the decision to go to a steel structure was made several possible types were thoughtof and they are: non-composite steel, composite steel and finally a castellated beam and girdersystem. A disadvantage of a steel structural system is the added depth of the members and thisreason was the critical reason why non-composite steel was first eliminated due it having deepermembers. To avoid interference with MEP systems it was key to keep the overall depth of thestructure to a minimum or to allow for adequate room for the said systems. Though castellatedbeams are deeper than composite steel members they have natural holes in them due to thedesign. It should also be noted that the overall building height was not changed so as to notimpact the architecture of the exterior and the building height limitations this was another reasonfor the two remaining systems.

The specification and range of the holes in size were looked at and compared to thedifference in thickness of the two remaining systems. It was concluded that the hole size was notlarge enough to run a decent size round duct, the composite floor would be better suited forrectangular ductwork and also you have more flexibility of turns in MEP systems but also awider range of MEP shapes that will work. So in conclusion from looking briefly looking atcomposite steel and castellated, composite steel is the better chose and will be used for the rest ofthe structural design.

Bay and Column Grid Layout

Since the original structure of Building 7 was Hambro joists on light gage stud bearing

walls and the lateral system was light-gage stud bearing walls and reinforced concrete it wascritical and obvious that the existing layout of a column/wall grid was not going to work, so anew grid needed to be created. A typical bay was also created as best that could be for repetitionand ease of construction throughout the floor plan.

Due to there being a corridor in the middle of the building a simple two bay layout withequal bay sizes was not going to work alone. After looking at the plans more carefully a primaryfactor in determining the bay sizes was the corridor walls. These walls provide a stopping placefor the typical bay. Two possible solutions came from this: an unequal size two bay layout whichone is wider or a double loaded corridor with two equal bays on each size. A simple design waslooked at for both to see how deep the systems may become. The diagram below shows the depth

of the two different layouts in the early stage.

Corridor No Corridor

Gravity Study and Redesign


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Taking into considerations this relationship it was determined that a double loadedcorridor was the best choice so that the bays on each side would be the same but also theconnecting beams would be smaller resulting in more ceiling cavity space for the larger MEPcomponents. In the figures below you can see the new grid and the typical bay without infill

beams.

Beam, Girder and Slab Design

From the developed bay layout the composite metal deck that forms the slabs would need

to span perpendicular to the infill beams, which is a maximum of 9-6 typical. The compositemetal deck was chosen from the Vulcraft Steel Roof and Deck Catalog. It was determined that a3VL21 composite steel deck was selected, with a light-weight concrete slab. This type waschosen to ensure a two-hour fire rating for the slab without requiring the use of fireproofing ofthe deck and also to help lower the sound transmission from one side of the slab to the other.This resulting design gives a total slab thickness of 6.25 with 3.25 of concrete above the top ofthe deck.


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When the gravity loads were applied to typical beams it was decided to have the beamsact compositely so to have the concrete deck assist in the shear and making the sections smaller.Shear studs sizes and quantity was determined by the provisions listed in 13th Edition of theSteel Manual. The load case that controlled in all of the gravity framing was 1.2D + 1.6L except

for the roof which used 1.2D + 1.6Lr + L. The figure below shows a 3-D representation of thegravity system along with the lateral braces on a typical floor.

After a size was selected for strength using Table 3-19 (composite W-shapes) in themanual during the preliminary stage, a Ram Model was then built so to optimize the gravitysystem at each level. Deflection of the beams was considered in the design process during theconstruction loading, much deflection would lead to the addition of extra concrete to the slab,and during the long term life of the structure

To create a more efficient design repetition is an important factor. By using fewerdifferent size beams and girders can cut down on material costs and reduces the amount ofcoordination necessary in the field while reducing the chance of a mistake being made duringconstruction. Member sizes were coordinated such that beams and girders in similar bays and insimilar locations on different floors were made same size while sticking to a limited number ofsizes for the large areas. The final gravity design based on the new bay layout resulted in lightW14 sizes for girders on the second through eighth floors while the roof had W18s as girders,typically. The infill beams were light W12 sizes on the second through eight floors while theroof had W14 sizes. The calculations for these designs can be found in Appendix C.


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ColumnDesign

The gravity loads in the building are carried by the slab and deck then to the beams whichcarry the load to the girders, in turn goes to the columns. The columns then take this load to the

ground, through the buildings foundation. This is the typical load path used when designing thegravity columns. The tributary area was found on each floor for a given column and the totalaxial load was determined after reducing the live load according to ASCE 7-05 Section 4.8 and4.9. All the columns were designed for the axial load and gravity induced moments determinedand were designed according to 13th Edition of the Steel Manual.

After a size was selected for strength using Table 4-1 (axial compression) and Table 6-1(combined axial and bending) in the manual during the preliminary stage then the Ram Modelwas used so to optimize the columns at each level and limit the different sizes of each column.To minimize architectural impact of the columns on the new grid all of the columns weredesigned to be no larger than then W12 sizes. Also the splicing of the columns was considered

for construction reasons. The resulting design was to splice the column at every second floorwhile the first floor started with a two story column due to the odd number of floors. As with thebeam design adjustments were made to increase repetition the column sizes so to cut down onthe number of different sections. The resulting adjustments gave a total of 6 different columnsizes used throughout the building for the gravity loading only; these are all in the W12.


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Final Gravity Layouts

This section of the report contains the final designs of a typical column row from floor toroof and also a typical bay design across the entire width of the building. The details of these

designs are listed in the drawing while the thought process was listed in past sections. The detailsinclude member sizes, orientations, studs, splice locations and dimensions. Please refer toAppendix C for a complete layout of the three different typical floor plans and details regardingthe column designs.

Typical Bay Layout


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Typical Column Layout


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Gravity Connection Designs and Details

When looking at the gravity design during the design phase connection issues wereconsidered and designs were adjusted to make connections simpler. This primarily relates having

the girders deeper than the beams so that a double cope and significant reduction in the beamsection did not occur. To make construction easier and faster single shear tab connections werechosen for the beam to girder connection. For the girder to column connection an extended singleshear tab connection was chosen. These two connections were looked at in the typical bay andresults, reasons for these connections, along with a sketch of the final typical connection isbelow. Refer to Appendix C for sample calculations of these designs.

Beam to Girder Connection

The reason for selecting the single sheartab is so that the beams dont need to be

lowered between two angles or plates and riskdamaging those items, this allows for bringingthe beams in from the side. The plate alsoallows for all plates to be welded in the shopalso the issue of not having to deal with boltingissues with the beam on the other side of thegirder. Based on the forces used to design thisconnection, overall design resulted in areasonable connection.

Girder to Column Connection

The reason for selecting the extendedsingle shear tab is so that the beams dont need tobe lowered between the column flanges andmaking the bolting process smoother, this allowsfor bringing the beams in from the side. A bottomcope was used though not absolutely needed justin case the construction doesnt allow for sideplacement for this is safer when placing with a

crane. The connection again allows for all platesto be welded in the shop thus saving on at fieldwelding. Based on the forces used to design thisconnection, overall design resulted in areasonable connection.


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Considered Lateral Systems for Building 7

Of all the different possible lateral systems most valid for high seismic regions, four werechosen and looked at to see their benefits and also disadvantages .the four that were chosen to belooked at from with a non-design format are: Special Concentric Braced Frames, SpecialMoment Frames, Special Plate Shear Walls and Buckling Restrained Braced Frames. It shouldbe noticed that only steel systems were considered. The reasons for this was to keep the entire oras much as possible of the structure as steel, keep the different trades to a minimum and also forsimplicity of construction coordination with trade issues. Listed below are the summaries of thefinding and at the end of this section will list the chosen lateral system to actually be designed.

Special Concentric Braced Frames

Special Concentric Braced Frames (SCBFs) were looked at due to their simplicity ofdesign and they are one of the most commonly used. They can have many differentconfigurations and this can be beneficial to try and work around the architectural limits. SCBFsthough tend to have inherent problems due to the vastly different compression and tensioncapacities of the braces. Also the size of the gusset plate can get rather large when the forces arehigh due to how the connection must behave. Finally even though they are man configurationsthe braces tend to get in the way unless a clear area in the plan is available for them.

Special Moment Frames

Special Moment Frames (SMFs) were considered as a possible alternative for they allowfor a very open floor plan and have a limited impact on the structure. SMFs also have aminimum number of members which will affect the cost and overall volume of steel in relativeterms. The best place for these in Building 7 to use their benefits would be around the perimeter.The down side to SMFs is that there are a limited number of approved connections, drift can bea major issue in controlling, and also the beams could be large and could occupy more than theceiling cavity.

Special Plate Shear Walls

Special Plate Shear Walls (SPSWs) were looked at for they tend to be very thin and can

be placed between walls easily without affecting the overall thickness of the wall. SPSWs werecreated when the gusset plates on SCBFs tend to get large and almost touch. The shear walls canbe either un-stiffened or stiffened with extra plates. On a disadvantage standpoint manyconfigurations of openings and stiffener configurations have not been tested and pose designissues especially in modeling for right now this issue can only be solved with a true finitemodeling.

Lateral Study and Redesign


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Buckling Restrained Braced Frames

Buckling Restrained Braced Frames (BRBFs) are a relatively new yet promisingsolution. This system has near equal tension and compression capacities which eliminate post-

bucking load imbalances commonly found in other braced frames. Depending on the style ofbrace it can behave as true pinned-pined members. The number of braces can be reduced due tothe capacity is almost equal in tension and compression, possible single brace per story perframe. BRBFs are not a proprietary system but their configurations and details of the assemblyand in some cases the connections are subject to US patent laws and recreation is limited to theholding companies. They tend to cost more than standard HSS or W-shapes. The lastdisadvantage is that the design of BRBFs involves some complexities in modeling and also inmanaging drift control in modeling.

Initial Lateral System Decision

After reviewing the different listed systems with their benefits and drawbacks it wasdetermined that the best system for the new lateral system is the Special Steel Concentric BraceFrame. The reasons for choosing this system are:

1. Most commonly used and a good place to start with the multiple bracing systems2. Initial available wall space for the frames to fit in so the lateral system does not interrupt

the architecture3. Better at controlling drift when compared to Special Moment Frames4. Multiple styles of bracing configurations to choose from5. Multiple ways to design and detail the seismic connections6. Doesnt require specialty or complex software to model like Special Plate Shear Walls

This system of Special Steel Concentric Brace frames will be worked with and designed indetail for the new lateral system of Building 7. The overall design as well as the process forlocating, designing, and detailing this system is described in detail in the next few sections of thisreport.


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Layout and Location of Lateral Elements

The initial placement of where the lateral system would be was based on the samelocation as where the original ones were at with the exception of that the original lateral system

was also around the elevator core. The small size of the elevator shafts do not allow for aneffective braced frame to be placed there for the average width of one of those would be only 10max. The east west direction had more limited space to place these due to the architecture of thebuilding when compared to the west side so it is likely that those frames will be larger since thereare less of them. It can also be seen that the original plan of including only one lateral system isbeing kept and a dual system is not being considered. The boxed areas in red indicate thelocation of the new lateral frames.


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Modeling Assumptions and Considerations

Once all the necessary seismic provisions were taken into account and seismic loads weredetermined, a lateral analysis and design was done using a combination of Ram Structural

System and Etabs, depending on what was being looked at determined the modeling softwarewas used. Etabs was used primarily used to verify and check torsion effects and the buildingperiods. The following modeling assumptions and requirements were taken into account for bothprograms.

The Main Lateral Resisting System was only modeled in the case of ETABS but for RamStructural Steel the entire structure was model, for Ram was used to optimize the gravitysystem.

A Rigid Diaphragm was modeled at every floor with the lateral load being assigned to thediaphragm.

Lateral forces were applied to the center of mass along with a calculated moment due to

accidental torsion. The mass of the structure was assigned to a Null Shell Property at each floor. This gives

us an approximate period from the modal analysis.

The Proper Load Combinations were generated and used in accordance to all relevantcodes.

The Braces of the SCBFs were assumed to be pinned at each end.

The Structure was assigned a fixed support at the base for all gravity columns

The lateral Columns were modeled with fixed bases to help with drift slightly also fixityis not hard to accomplish.

PDelta effects were automatically taken into account in the model and ASCE7-05Conditions for modeling P-Delta effects were considered.


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Lateral SCBF Design

To design the new lateral system of Building 7 the new building lateral loads listed in theprevious sections were taken and placed into the computer model Ram Structural Frame and also

at times Etabs was used to verify the accidental torsion components as the design changed. Thelateral forces applied to the buildings diaphragm at the center of mass. Initial sizes were chosenso to allow the program to perform its analysis, these sizes were chosen based on what finaldesign might be but due to early stages it was more of a hypothetical guess.

Since moving the building to a high seismic zone and the fact that the seismic loading clearlycontrols additional special load cases per AISC 341-05 and ASCE7-05 were used along with thestandard combinations. Listed here are a few of the primary special required load combinationsof the many overall load combinations that were inputted in the model.

1.4(D +F)

1.2(D+F+T) + 1.6(L+H) + 0.5(LrorSorR) 1.2D + 1.6(LrorSorR) + (L or 0.8W)

1.2D + 1.6W+L + 0.5(LrorSorR)

(1.2 + 0.2SDS)D + QE+L + 0.2S

0.9D + 1.6W+ 1.6H

(0.9 0.2SDS)D + QE+ 1.6H

After all advanced modeling criteria were placed into the model for both the MAE integratedrequirements and also according to the code. The analysis was performed and a design check wasmade on the initial members. The members that failed under loading were increased in size andthe model analysis was repeated and checked once again. This process was repeated till all

members were designed sufficiently for strength. The capacity of each member was taken tobetween 60-75% if design strength for all lateral members.

Once all of the members were satisfactory for strength requirements drift issues were lookedand calculated. It was determined that the lower four floors met the seismic drift requirement butthe upper levels were exceeding the drift limit. Since drift was over the allowable it wasnecessary to try and bring down the drift on the upper floors. Three options were considered inincreasing the member sizes to control the drift, they are:

Increase beam sizes

Increase column sizes

Increase brace sizes

All three of these options were tried but the one that had the most significant effect wasincreasing the brace sizes for they are the key component of the lateral SCBF system. Columnsizes were also played with slightly also if just the drift needed to be lowered slightly. Modeliterations were completed and rerun after each change of member sizes so to make ensure thepossible change COM and COR were taken into account.


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In the end it was clear that the upper five stories were controlled by drift for the capacity ofthe member was only between 15-25% of its design strength. It can be seen in the figure belowthat the brighter the colored members are the closer they are to their design strength and anindication where drift was the deciding design factor. This result is reasonable for the lower

floors are typically stiffer and have less load acting on them to contribute to drift. Where at theupper floors are less stiff.

As the members were being designed special requirements were followed per AISC 341-05 and ASCE7-05 so to ensure that the lateral system behaves ductility and has hystericdamping. All members were limited so that local buckling requirements were acceptable perAISC 341-05. Table 1-2 and Table 1-4b was used to verify all columns and braces in the SCBFdesign met this requirement.

The member sizes in the frames were considered and limited were at all possible so to fitwithin the barrier walls between the apartments. The vertical members of the frames were allselected to be either W12 or W14 shapes, each frame was limited to one W range so that thesplicing of the columns were easy for the interior flange to flange dimension is the same.Rectangular hollow structural steel sections were used as the diagonal bracing members so the

bending strength was the same about both axes and thus the brace could buckle equally abouteither direction during an earthquake. The sizes of these members range from an 8 to 10 inchwide with a nominal thickness of 5/8 inch or an equivalent W-shape with the same cross-sectional area was used. Three sample elevations are shown on the next page to represent atypical SCBF in both the N-S and E-W direction. Please refer to Appendix D for more detailedframes and also calculations.


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Typical SCBF Lateral Layouts


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Lateral Detailing

Since SCBFs have an R=5 it is import and critical, not to mention required to do seismicdetailing if the lateral system. Seismic detailing of steel SCBF is controlled per IBC 2006 and

also AISC 341-05 Specification. The sections of the newly designed lateral system, SCBF, werechosen for they have the larger effect on the overall behavior of the system. The areas that werelooked at were:

Brace to beam connection

Column splice

Inverted V beam

Brace to beam to column connection

The column to foundation

The codes were followed resulting in a represented typical connection and member detailing

of each. The resulted of the studied areas are listed in this section and the region where each wasdesigned at and typically located can be seen in the figure below.


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Inverted V Beam

The inverted V beam and brace configuration at the top of each frame was designedsimilarity to the lower brace to beam connections with the exception that the beam at this level

had additional requirements. The beam was designed as continuous and as if the bracing is notthere for gravity loads. Also it was designed to take the vertical unbalanced load from 100% ofthe tension expected yield strength and 30% of the compression brace nominal strength as perAISC 341-05 Section 13.4. Finally the beam top and bottom flanges were braced where theintersection of the braces met.

It should be noted that the seismic steel code from 2002 allowed the exception of the topbeam on a braced frame where a V configuration ends in the middle of the beam on the rooffrom taking the unbalanced load. The new 2005 code does not permit this and was needed to beconsidered.


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Column Splice

AISC 341-05 Section 13.5 requires all splices be located in the middle third of thecolumn clear height so to prevent a story mechanism. This section also requires that the splice

shear strength can carry the strength of the lesser two column shapes in shear. Theserequirements were implemented in the column splice design, to which a plate on each side wasadded to carry the shear demand and a CJP was used to carry the flexural capacity of themembers. Also all column splices were located at the mid-height of the clear column.


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Brace-Beam-Column Connection

When this connection was being designed the Uniform Force Method was used todetermine the length and height of the gusset plate so that there were no moments on the three

connection interfaces. The connection along with the gusset plate was designed to meet AISC341-05 Section 13. The gusset plate is designed so to develop a plastic hinge and buckle out ofplane, it also has to be able to take the expected capacity of the brace in tension and also incompression. Buckling limitations were checked and followed so that the plate behaves correctlyunder severe loading. A Grade 50 steel plate was used to help cut down on the overall size andthickness of the plate which is allowed in AISC 341.

The gusset plate was designed so that the plate was welded to the beam in the shop forthis approach is simpler for infield setting. The beam to column connection part was designed asa simple shear table for the moment was low but also because the relative lengths of the gussetplates would take and resist the moment. The brace had to be reinforced around the connection

interface due to the slot taking away from the cross-section and also an issue with shear lag. Thedrawing shows the details of the design; the brace connection would be repeated on the lowerhalf of the beam but was omitted for clarity of the connection.


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Brace - Beam Connection

The gusset plate was designed to meet AISC 341-05 Section 13. The gusset plate isdesigned so to develop a plastic hinge and buckle out of plane, the gusset plate has to be able to

take the expected capacity of the brace in tension and also in compression. Buckling limitationswere checked and followed so that the plate behaves correctly under severe loading. A CJP wasused so to cut down on the length and size of weld needed along the beam. The brace had to bereinforced around the connection interface due to the slot taking away from the cross-section andalso an issue with shear lag. Finally the stiffener plates were required so that the brace didntbuckling in the center but allow the brace to yield below where the brace ends. The drawingshows the details of the design.


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Column Base Plate

To obtain a fixed end at the columns base of the foundation in the lateral system the baseplate and anchors need to be able to resist moment. This can be achieved by using a thick base

plate that wont bend. The column is then CJP welded to the plate to endure it is rigid andsufficiently strong. To ensure a rigid action the plate had to have a larger moment of inertia (I)than the column, to achieve this anchor rods were placed at the outer edge of the plate to keep theI larger. These bolts were than determined that a through nut would be best so to be able to placethem in during the foundation pouring.

A space was needed so to be able to grout the plate to the foundation as one, also a shearwas placed on the base plate to take the shear so the anchors didnt have to carry it all. As it canbe seen in the drawing it was necessary to add a plate for the gusset plate t rest on and act as itshould. Also since the ground floor is inhabited the base plate could need to be counter sunkinto the foundation so that it does not interfere with the architecture and floor space. For this

Connection and detail Ram Base Plate was used to design the elements based on the correctcorresponding material properties and the forces inputted.


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Seismic Drift

Drift is a serviceability issue and should be limited as much as possible while stayingwithin reason. The allowable seismic story drift was calculated using ASCE 7 Chapter 12. Story

drift for each floor is calculated per equation 12.8-15 and allowable story drift is per equation12.12-1. Drift was looked at and limited so to stay within the allowable. Drift was a controllingfactor in the lateral system and iterations were done with the design so to get acceptable valuesas code dictates.

The deflection values were taken from Ram Structural System at the center of mass ateach floor which is permitted by ASCE 7-05 Section 12.8.6. The change in deflection from onestory to another was obtained to track any possible jumps and compare these changes against theallowable values. After examining the deflections and working on limiting it the final design itcan clearly be stated that a steady increase of deflection going up the building. No story in eitherdirection fails in meeting the allowable drift. The tables below show sample calculations of the

drift.

Drift and Displacement Calculations for SCBF N-S Direction

Story Height (Ft.) hsx (ft.) Story Displacement (in) xe (in) x (in) a (in) Final Results

Roof 10 10 3.236 0.494 2.257 2.400 Good

8 10 10 2.742 0.487 2.223 2.400 Good

7 10 10 2.255 0.441 2.016 2.400 Good

6 10 10 1.814 0.433 1.977 2.400 Good

5 10 10 1.381 0.364 1.663 2.400 Good

4 10 10 1.017 0.388 1.774 2.400 Good

3 10 10 0.629 0.275 1.256 2.400 Good

2 10 10 0.354 0.257 1.175 2.400 Good

1 10 10 0.097 0.097 0.441 2.400 Good

Drift and Displacement Calculations for SCBF E-W Direction

Story Height (Ft.) hsx (ft.) Story Displacement (in) xe (in) x (in) a (in) Final Results

Roof 10 10 3.402 0.483 2.316 2.400 Good

8 10 10 2.919 0.441 2.115 2.400 Good

7 10 10 2.478 0.487 2.335 2.400 Good6 10 10 1.991 0.478 2.291 2.400 Good

5 10 10 1.514 0.398 1.907 2.400 Good

4 10 10 1.116 0.422 2.022 2.400 Good

3 10 10 0.694 0.299 1.432 2.400 Good

2 10 10 0.396 0.280 1.341 2.400 Good

1 10 10 0.116 0.116 0.557 2.400 Good


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Soft Story

To ensure that there are no soft stories which would result in vertical irregularity,calculations were computed to verify if any exist within the new system. The tables below verify

that the final design does not have a soft story issue and therefore ELFP is still valid.

SoftStoryCheckforSCBFNSDirection

Story Story Drift Drift Ratio0.7x the

Story DriftRatio

0.8x theStory Drift

Ratio

Avg. Story DriftRatio of Next 3

StoriesSoft Story Issue

Roof 0.494 0.0494 0.0346 0.0395 No

8 0.487 0.0487 0.0341 0.0389 No

7 0.441 0.0441 0.0309 0.0353 No

6 0.433 0.0433 0.0303 0.0346 0.0474 No

5 0.364 0.0364 0.0255 0.0291 0.0454 No

4 0.388 0.0388 0.0272 0.0311 0.0413 No

3 0.275 0.0275 0.0193 0.0220 0.0395 No

2 0.257 0.0257 0.0180 0.0206 0.0343 No

1 0.097 0.0097 0.0068 0.0077 0.0307 No

SoftStoryCheckforSCBFEWDirection

Story Story Drift Drift Ratio0.7x the

Story DriftRatio

0.8x theStory Drift

Ratio

Avg. Story DriftRatio of Next 3

StoriesSoft Story Issue

Roof 0.483 0.0483 0.0338 0.0386 No

8 0.441 0.0441 0.0309 0.0353 No

7 0.487 0.0487 0.0341 0.0390 No

6 0.478 0.0478 0.0334 0.0382 0.0470 No

5 0.398 0.0398 0.0278 0.0318 0.0469 No

4 0.422 0.0422 0.0295 0.0337 0.0454 No

3 0.299 0.0299 0.0209 0.0239 0.0432 No

2 0.280 0.0280 0.0196 0.0224 0.0373 No

1 0.116 0.0116 0.0081 0.0093 0.0333 No


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Torsion Effects

Center of Mass and Rigidity

For each diaphragm the center of mass (COM) and center of rigidity (COR) werecalculated so that the exact location of the resultant story force was is located. These two pointson the diaphragm determine how much eccentricity there will be, which in turn will cause atorsional moment on each floor. A sample calculation was performed on a typical upper levelfloor plan. The figure below shows the location of both. The orange dot is the COM and the reddot is the COR.

These locations seem valid for more of the mass is on the west side while the mass isnear equal on the north and south side. The stiffness in the east-west direction is equal for thefour frames all have the same stiffness. In the north-south direction there are more frames whichshift the COR in their direction which is what is happening.

Same calculations of these values were done and are very close to the Rams. Thesenumbers were used for the torsion calculations listed in the next segment. The values are almostthe same for each floor with respect to each other due mostly to each floor being relatively thesame layout and plan area except for the first floor. Values to these can be found in Appendix D.


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Inherent Torsion

When the center of mass and the center of rigidity are not located in the same exact spotthen there is inherent torsion acting on the diaphragm which is carried to the lateral system.

ASCE 7-05 Section 12.8.4.1 was followed when looking at this issue and it was determined thatthe building had a rigid diaphragm. The Y direction had a close COM and COR resulting in asmall torsional moment but the X direction had a larger torsional moment due to the COM andCOR being farther apart. An analysis was performed to determine the torsional shear on eachstory caused by wind forces.

Accidental Torsion

Since Building 7 is now in a Seismic Design Category D it is required to consideraccidental torsion now. ASCE 7-05 Section 12.8.4.2 was followed to calculate the accidentaltorsion at each story on the structure when a 5% eccentricity is created in each direction

individually from the center of mass. When calculating the Accidental torsion an amplificationfactor needs to be multiplied to this value. ASCE 7-05 Section 12.8.4.3 was followed anddetermined, in the cases where it was less than one a value of 1.0 was used and a max of 3.0could be used. It was determined though when looking at the data and performing thecalculations that the amplification factor for the structure was all under 1.0. Values to thesecalculations can be found in Appendix D.


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To meet the requirements of the integrated class with advanced topics covered ingraduate level classes, several key areas and sections of material were utilized in this structural

study and redesign. All of the results and details can be found throughout this report in theprevious sections. The reason why this was not grouped separately was because it was morerelevant to place those sections with the corresponding section of the report it deals with. Listedin this section is a brief overview of what was used for the MAE required integration.

Advanced computer modeling techniques were used so to obtain more accurate resultsand include more variables when the corresponding codes required it.

The study and design of both gravity and lateral connections were looked at for the newstructural steel system.

By moving the building to a high seismic zone a more in-depth lateral analysis andspecial criteria had to be determined when designing the MLFRS.

Integrated MAE Work


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Top Story Brace Configuration

When the top stories of the Braced frames were laid out it was noticed that an inverted-Vwas going to be present. Since this configuration lead to massive beams as it is shown in theSeismic detailing section of the report it was realized that this configuration at the top isnt themost optimum for the beam itself is deeper than the total thickness of the ceiling cavity. Analternate configuration was considered and the alternate is a single story X configuration so thatthe members did not frame into the mid-span of the beam creating a requirement for theunbalanced load in the brace members. This alternate configuration allowed for the same style ofgusset connects along the column beam interface as before on the lower levels.

It was determined through rerunning the model with the new configuration that the sizesof the members were able to be reduced to HSS9x9x5/8. This is mainly due to their being

more brace on that level to take the shear. The top beam was able to stay at a W18x60. Theconnections were not looked at in detail but since the member sizes went done it can be said thatthe gusset plate sizes went down as well. This new configuration has a small positivecontribution to drift for it reduces it by a small amount but isnt a large contributor overall. Thereis a reduction in the price of this configuration for the top beam is smaller and the larger massiveconnection at the top is replaced by four small connections. The figure shows the sizes of themembers for this new configuration.

Structural Alternatives


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Alternative Brace Frame Type

Since the gusset plates are getting thick and are requiring large welds along with thebraces needing to be reinforced at the connection interface there could be a more efficient

approach to the lateral system can be considered. Based in the information listed at the beginningof the lateral Study the next best alternative would be to look at the Buckling Restrained BracedFrames. With BRBF brace members can act as a true pinned connection with the Stare SeismicLLC brand, which uses a pin connecting it to the gusset plate. The gusset plates themselves tendto be smaller for they tend to have lower forces because of the R value BRBF being a 7 or 8depending on if the beam column connection takes moment.

Even thought BRBFs are not a proprietarysystem their configurations and details of the assemblyand in some cases the connections are subject to USpatent laws and recreation is limited to the holding

companies. This does not exact fit with the structuralgoals of eliminating the propriety systems but thebenefits especially for building 7 would be worth it.The BRBF brace members tend to be more expensivethen the standard HSS or W-shapes SCBF but theconnection terms and labor related to making theSCBF connections would be cheaper. The lastdisadvantage is that the design of BRBFs involvessome complexities in modeling and also in managingdrift control in modeling.

The pictures and figures below show the standard details of BRBF systems and it can beseen when comparing them to the seismic connections that were design for this thesis in thelateral detailing of this report.


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Structural steel may be very durable but when it comes in contact with high heat from afire its strength can rapidly decrease and speed up the failure. The original building was bearing

walls and Hambro Joists, these systems did not require fireproofing in large volumes but insteadhad complex UL rated assemblies had had to be met to ensure the correct fire rating for thedifferent sections.

When the gravity system was designed the deck was chosen and designed such that thedecking did not require spray on fireproofing. This decision can and will save an enormous aboutof fireproofing for not having to cover the decking cuts down on the overall area. Even thoughthe deck doesnt need fireproofing the steel beams, girders and columns do require it. Uponlooking into the different types of fireproofing it was concluded that a cementitious plaster basedfire proofing with a combination of Portland cement and lightweight aggregates, vermiculite andperlite. Typically the columns get a much larger thickness for they are more critical. It can be

seen in the table below the overall cost of the fireproofing for the gravity system when the deckis sprayed and when it is not. The overall savings is $1.14 when the deck is designed to have nospray of fire proofing. Note these numbers also include the materials costs for the steel, concreteand deck, though the prices of these materials were the same cost as noted in RS Means.

Level Area SOFPforAll SOFPExceptDeck

Roof 14750 $ 378,337.50 $ 356,950.00

Floor8 14750 $ 310,487.50 $ 294,262.50

Floor7 14750 $ 310,487.50 $ 294,262.50

Floor6 14750 $ 310,487.50 $ 294,262.50

Floor5

14750

$

310,487.50

$

294,262.50

Floor4 14750 $ 310,487.50 $ 294,262.50

Floor3 14750 $ 310,487.50 $ 294,262.50

Floor2 14750 $ 310,487.50 $ 294,262.50

Floor1 12621 $ 265,672.05 $ 251,788.95

TotalCost $ 2,817,422.05 $ 2,668,576.45

SavingsTotal $ 148,845.60

SavingperSF $ 1.14

The lateral system would also need to be sprayed for it is all steel. A direct comparisoncan not be made for everything needs to be sprayed and the original was an assembly wall. Still

though the lateral system would be costly to fireproof due to the large members and also that thegusset plates are very large resulting in more area to protect.

Fire Proofing


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Due to the change in location and also the change in the structural system it can clearly

be seen that the foundation system would be affected. The original system had bearing walls andshear walls which resulted in more strip footings than spread footings. The new system has morecolumns which will mean that more footings are required, however since the new site has abetter soil conditions less piles may be needed. This system was not looked into detail for thedepth of this thesis but certain areas were looked at in a more general aspect to see how thingswould be affected.

Code Requirements

Due to the change in location to a site with a Seismic Design Category D, special

requirements need to be met with the new location. ASCE 7-05 Chapter 19, Section 19.2 needsto be followed so to incorporate the soil-structure interaction of the foundations can beconsidered and modeled. The foundation requirements for SDC D as controlled by ASCE 7-05Section 12.13.6 which tells that the foundation must be tied to the piles and caps along with thecorrect procedure to design the different styles of foundations. Section 12.1.5 tells that thefoundation must be designed to accommodate the dynamic ground motion, structure movement,the shifting of the soil creating stresses on the soil, and also energy dissipations requirements.

It is because of these requirements in Chapter 12 and 19 that the foundation design wasnot looked at in details and very simplified assumptions were performed in the next segment ofthis report for the code requirements of the foundation system is beyond the scope of this thesis

study.

Schematic Design of the Foundation

In this schematic design of the foundation only the gravity loads were considered for thecomplexity of the seismic lateral provisions related to SDC D was beyond the scope. The each ofthe columns would require a separate foundation except with the columns on each side of thecorridor for since they are close a shared foundation would be best for them. Gravity loads were ltaken from the Ram Structural Model and from here a foundation area was determined based ona soil bearing capacity of 4000 psi with this information an area was determined for the

foundations.

For the foundations under the lateral system exact sizes were not calculated but it is safeto say that strip footing would be present from one side of the frame to the other. Beneath theseon the ends would be the caisson grouping with the cap connecting it to the footing. This is thesame configuration that is currently being used but since the forces are higher it very well couldmake this foundation larger especially on the uplift design.

Foundation Implications


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When looking at the new schematic foundation plan on this page as compared to theoriginal found in Appendix G it is clear to see that the new steel system requires more and largerfoundations also it can been seen that some of the foundations are very close to touching and intwo cases they are overlapping creating a complex shape. The table below also shows the sample

calculations made for the gravity schematic design.

Load(Kips) SoilBearing(ksf) Areaneeded(sf) Sizes(ft.)

TypicalExteriorColumn 355.00 5.56 63.90 8

TypicalInteriorColumn 324.00 5.56 58.32 8

CorridorbendColumn 600.00 5.56 108.00 10


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Acting Forces on the Foundation and Overturning

Overturning issues in foundations arise when the forces on the lateral elements aregreater than the weight that the lateral element. Also the soil bearing capacity has an effect on

overturning by how much load it can take before a strength failure or a bearing failure occurs.When the lateral moments and axial forces are not balanced out by the weight and soil capacity,then the foundation wants to start and tip over inside the ground. One end tends to lift up whilethe other often likes to sink into the soil. Since seismic foundation design was not considered andthe complexity of the structure it is hard to tell if the new foundation will have overturningissues. However the figure below shows how the forces are interacting with each other at thefoundation level. The red loads are trying to force the foundation to rotate as the blue loads aretrying to resist the movement.


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When looking at the structure of a building the cost of the structure plays a major impact

in the overall selection of a system but also helps set the price of the buildings total cost. Theoriginal structure cost $2.93 million when Building 7 was located at University of Maryland.Since the building was moved to San Diego now a direct comparison of just cost for changingthe structural system to a steel system is hard and not necessarily a good representation.

High seismic regions have a tendency of having a high structure cost due to the lateralcomplexity of the connections and also the mass of the members. Also west coast practices havedifferent common in-field techniques from east coast especially regarding welding. Welding inthe west coast is more regulated and all welds are required to be inspected. This will result inhigher costs in labor. All these factors and many not mentioned are a large contributor to theoverall cost. Because of these implications it is clear and reasonable to state that west coast

building are more costly to design and build, the structure alone is more costly and whendesigning in the west coast a different way of thinking is needed when designing for structuralcosts increase and more of the overall budget will be in this part of the building as compared tothe east coast.

Additionally there are other designs a structural engineer must perform that will increasethe cost. These include but are not limited to: mechanical system attachments, non-structuralarchitectural components and walls systems-both interior and exterior.

Cost Considerations


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After completing the structural depth study of redesigning the entire system to steel and

moving Building 7 to San Diego, CA to look at the effects and implications of a high seismiczone it was determined that the structural goals were met. It was clear that a structural design insteel can be developed to carry the loads required by code, without a large impact on otheraspects of the building. This while the building height did not need to be changed in order to fitthe gravity beams based on the study, it is recommended that in the end the height of the floorcavity should be increased for there is still limited room left after the steel. The double loadedcorridor allowed this to be more acceptable for there was more space in the corridor ceiling butany MEP systems going to the adjacent bays would need to be carefully designed to fit into thesmaller remaining space.

For the lateral system redesign the overall process and goal was met for all the required

checks and procedures for designed in an SDC of D were performed. The seismic loading wasdetermined to be very high and thus controlled the overall lateral design for the wind didntchange significantly in the move to San Diego. A computer model was created and the lateralloads and load combinations were inputted and the lateral system as designed. In the end thelateral frames were designed to meet the requirements for strength and drift. The resultingmembers of the SCBFs were on the large size but considering the magnitude of the force.

The final lateral system design is acceptable for Building 7 and is more efficient andrecommended that the alternatives be considered in the future and further developments for theycan help the lateral system for the better. While this layout is acceptable it required a redundancyfactor of 1.3 because there was no perimeter framing in each direction, also the inherent torsion

was also large for the limited space to place the SCBFs within the plans which would not affectthe architecture. For this reason it is recommended that further developments of perimeter lateralframes be used to reduce the redundancy factor and also try and limit the torsion more.

Both gravity and seismic connections were looked at for this study. The two gravityconnections were both in the end determined to be shear tab connections for the ease and speedof construction of these connections made them ideal. For the lateral seismic connections typicalconnections for a SCBF were considered and designed. In the end the seismic connectionsbecame very complex and large due to the required forced for the members to behave correctlyunder seismic loading.

Lastly fireproofing issues and cost savings from not fireproofing the decking wereconsidered along with an alternative brace configuration at the top of the lateral frames. Thealternative configurations was in the end a better choice for the members were smaller and workbetter with the architecture along with the cost of this configuration was less. Another alternativeor consideration after completing this thesis report and study is that due to drift being an issuewith the SCBF that an alternative study of Buckling Restrained Braced Frames would be a validchoice for the reduced connections and better control of under loading as proved by theHysteresis Loops.

Structural Design Summary


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Structural Goal Evaluation

Goal 1: Design an overall structure made of steel and has limited use of propriety systems.

This goal was achieved for the design is using rolled shaped members and plates. Itshould be noted though that the other systems not considered in this report may have tobe propriety systems but the major contributors to the structural system are not now.

Goal 2: Design a gravity system that does not require a change in the building height while stillbeing acceptable.

This goal was achieved with the new design by using a double loaded corridor whichgave room along the corridor to run the MEP systems. This goal has its disadvantages for

the space is still limited and would most likely result in an inefficient design of the MEPsystems. In the end this works but the ceiling/floor cavity should still be inc

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